With the Cathay Circle Theater being in such a central and important location, the attraction should not must be any attraction, but really be something special. After all, it might become the symbol for the new DCA.
Here are three possiblities:
1) It be about Walt -- Some kind of movie or museum.
2) It be about Mickey Mouse -- Walt love to say it all started with a mouse.
3) It be a really spectacular AA show that kids and adults would enjoy, maybe with Mickey and the fav 5 or something.
I really like the GMR at Disney Hollywood Studios, but it has suffered because the movies it featured are now dated. This attraction really has to be timeless and not a promote what is popular today kind of place.